Method of concentrating brines



Patented Sept. 18, 1923;

uni-"ree srares" PATENT orrice.

HARRY w. Mensa,[orsurnlvronnonrvnnsrry, canrronnra ASSIlZGNOR 'ro WEST END CHEMICAL COMPANY, OF OAKLAND,

FORNIA.

No Drawing.

T all whom it may concern:

Be it known that I, HARRY WV. MoRsE, a

citizenof the United States, residing at Stanford University, in the county of Santa Clara and State of. California, have invented a new and useful Method of Concentrating Brine's', of which vthe following is a specification.

This .invention 'relates to -the concentra-' tion of .brines COHliflll'llllgStL-ltS of potassium and sodium, and particularly tothe concentratlon of Sea'rles' Lake brine, occurring atSearles Lake, Californimthe main object of 'theinvention being to provide for a rela tively high concentration of potassium salt by means of-solar evaporation. p The brine of Searles Lake has the inmiapproximate composition in grams of salt per liter: V

and this'brine-has Laternperature of about '21" O. as it ispumped fromthe wells.-

At the temperature at which it is pumped from the salt-body any concentration I by solar evaporation results in the formation of a solid salt (Glaserite) containing potas- Lake, concentration. can be carried on to some extent without the formation of solid salts containing potassium, but only a comparatively slight concentration can be attained inthislwayv;

i the boiling pointof water in the presence of follow Athig 'her temperatures, such as-a-refound for a considerable partof the year at Searles sulfate can be removed from the brine is by CALIFORNIA, A CORPORATION OF CALI- METHOD OF CONCENTRATING BRINES.

' Application filed September 6, 1921. Serial No. 498,869.

solid sodium chloride has the fOllOW'lllgltlP- proximate composition in grams per liter:

Potassium chloride 65.0 sodiumfchloride 270.0

Sodium bibo rate 21; 0 Sodium carbonate s. 50.0 Sodium sulfateh 35.0

After treatment in this way thebrinercan be concentrated at a minimum temperature of 21- C. to a potassium chloride content of over 100 grams per liter without the separa tion of any solid ipotassium' salt. w

When a solar pond has once been started:

WltlI-bI'lIIB which has been treated "for' the removal of; sulfates, as described, and after evaporation has proceeded "sufliciently' itO' raisethe carbonateto a'high concentration, saylOO grams perliter; raw brine, which has: not been previously treated in any way, can

be addedto thebrine already concentrated,

Without separation of any solid salt of po tassium. 1' A ForS-example, after heat-treatment with sodium' chloride' and after. exposure to solar:

evaporation, a concentrated brine may contain:

Grams per N, U literp,

Potassium chloride 105.0v Sodium, chloride 200.0 Sodium carbonate o 110.0

Sodium 1 sulfate; 58.;0 Sodium biborate 35,0

Raw brine can now be added toithis :pond in volume sufiicient to diluteto 90 grams of potassium chloride per liter. After a-few days of evaporation the total volume will rev turnrtoo-v the original concentration-of 105 I have foundthatfit is possible to obtain concentration :to a'much higher point 1 control of the sulfatecontent of the-brine; so asto decrease the "concentration of theamount of solution containing potassium chloride at the stated concentration is obtained.- p a Instead of raw brine, that is to say .brine taken directly from Searles -Lake, it: is also possible under certain conditionsr to use brine which has been previously evaporated in preliminary ponds at sufliciently high temperature to prevent the loss of potassium by the formation of solid potassiun'i salts, such partially concentrated brine being added to the prepared pond in the same manner as above described in the case of the addition 01" raw brine. In this connection it may be stated that the brine pumped from the body of liquid at tiearles Lake at a considerable depth below the surface is at a temperature of about 21 C. and could not be concentrated without loss of potash this temperature. in some cases, however, it is desirable 'to take the brine from shallow ponds after brine containing grains of potassium chloride per liter is then removed to the prepared ponds for dilution, such'prepared ponds having a low content'of sodium su].-- fate and a high content of sodium carbonate by reason of the preparatory treatment above described. p 7 i 1 A brine containing sodium and potassium salts in the proportions of Searles Lake brine. can be concentrated to over 100 grams per liter of potassium chloride without loss ofpotassium by formation of solid potassium salts provided the sodium carbonate COUCGH- tration is kept at a high figure and provided the minimum temperature of the pond does not fall below 21 C. V

Where it is desired to produce a crude salt as high as possible in potassium by solar evaporation, it is evidently of advantage to be able to concentrate the brine in preliminary ponds up to 100 grams of potassium chloride per liter. then moving this concentrated brine to other ponds in which it is evaporated to approximate dryness.

lVhen the original raw brine 'ofSearles Lake is evaporated to dryness the dry salt will contain approximately:

Potassium chloride 14.0% Sodium chloride 47,0 Sodium biborate 4.5 Sodium carbonate '15.5 Sodium sulfate ii i 19.0

A brine which h as been concentrated with control of the sulfate content up to- 100 grams of potassium chloride per liter will give a dry crude salt of the following approximate composition:

;A brine containing sodium and potassium salts .in the proportions of Searles Lake brine can be concentrated to over 100 grains per liter of. potassium chloride without loss of potassium by formation ofsolid potassium salts provided the sodium carbonate concentration is kept at a high figure and provided the minimum tei 'iperature of the pond does not fall below 21 C. V

Under the conditions of pond operation described. above sodium sulfate is removed fronrthe brine in the form of a double sulfate-carbonate of sodium. This substance slightly soluble compared with either the sulfate or the carbonate, when the concen-: tration of either sodium sulfate or SOdIUm' carbonate in the brine ishigh. If the sodium sulfate content of-t'he brine is made high, the double sulfate-carbonate will .crystallize out until the sodium carbonate content of the residual brine is low. 1 If the sodium carbonate content is high, the doubleYsuL' fate-carbonate will crystallizeout until the sodium sulfate concentration of the residual brine is low. I i i 4 For the purpose of concentrating such a brine in potassium, it 'is desirable that the"sodium sulfate content of the brine be kept as low as possible. Thiscanbe attained by keeping the sodium carbonate high. 1 v V .1 1 i The purpose of the preliminary treatment of the brine is, therefore, to make a brinelow" enough in sulfate so that it can be carried to a high concentration of sodium carbonate by solar evaporation without separation of solid potassium salts.

Once the treated brine has been concentrated to a high carbonate content, raw brine can safely be added. as the highcarbonate content causes the separation of thedouble sulfate-carbonate and the sulfate coutent of the brine is in this way kept low.

VVhatIclaim is: i

1. The 'method of treating. Searles Lake brine which consists in making a prepared brine by removing a portion of the sulfate content thereof by heating the brine inthe presence of solid sodium chloride. then subjecting the brine to solar evaporation to produce a brine high in carbonate, and then adding brine containing substantially the full potassium salt content of the Searles Lake brine concentrated by preliminary evaporation atsuch a temperature as will prevent the. separation of solid potassium salts. to the prepared brine. and again evapcratingto restore the high carbonate content of the brine. 2 I

2. The process for the concentration of the potassium content of Searles Lake brine which'consists in removal of sodium sulfate from the brine by heating the brine in the presence of solid sodium chloride, evaporating the treated brine to a high carbonate content and then adding, in'successlve stages, raw brine, partially concentrated by preliminary evaporation at such a temperature as Will prevent the separation of solid potassium salts, to the brine high in carbonate in such amounts and in such manner that the high carbonate content of the brine is at each stage restored to 1ts orlginal value before further addition of raw brine;

3. The process for the concentration of potassium salts 111 a Searles Lake brine coniprlslng a preliminary stage of removlng sulfate from a portion of the total volume bonate content, and then adding to the brine so evaporated, a Searles'Lake brine, then continuing the evaporation in a series of stages adding a Searles Lake brine after each stage as the sulfate is precipitated and as the carbonate content is restored by the evaporation.

4:. The method of removinga part of the sodium sulfate from Searles Lake brine Which consists in heating the brine in the presence of solid sodium chloride to a temperature approaching the boiling point of Water, and maintaining this temperature for from one-half hour to two hours.

In testimony whereof I have hereunto subscribed my name this 8th day of August,

r V HARRY W. MORSE. 

